Raytheon Aircraft is working on an in-house sound-reduction package that aims to lower the noise levels by about 5 db in the Premier I cabin. The interior package will start being installed on the production line in the fall and be retrofittable at no charge to customers, the company said. The package will consist of hydraulic pulse dampeners, a small increase in the space between engines and mounting pylons, tuned mass absorbers installed in the engine mounts, new engine fan shroud and various interior treatments.